PURPOSE: In order to reduce the rate of conversion to an open cholecystectomy, and to avoid the retention of bile duct stones, it is important to detect a choledocholithiasis prior to a laparoscopic cholecystectomy. The aim of this study was to compare the diagnostic accuracy of endoscopic ultrasonography (EUS) with endoscopic retrograde cholangiopancreatography (ERCP) in 150 patients who had an intraoperative cholangiography and choledochotomy with a choledocholithiasis performed. METHODS: Between January 2001 and February 2002, 150 patients who underwent an ERCP or EUS performed preoperatively and a cholecystectomy with intraoperative cholangiography or choledochotomy consecutively performed at the Inha University Hospital were reviewed. RESULTS: An ERCP was performed in 119 patients, and an EUS was carried out in 67 patients. Thirty six patients had both performed. The ERCP failed in 17cases (14.3%). The EUS identified the bile duct in all cases. There were five ERCP related complications (3 pancreatitis, 2 cholangitis), but no complications were encountered when using EUS. In 62 patients (41.3%), a choledocholithiasis was found. ERCP had a sensitivity of 89.5%, a specificity of 84.4%, a positive predictive value of 87.8%, and a negative predictive value of 86.4%. EUS showed a sensitivity of 88.9%, a specificity of 84.7%, a positive predictive value of 66.7%, and a negative predictive value of 95.3%. Concordance of ERCP and EUS was obtained in 90% of cases. CONCLUSIONS: EUS appears to be safer, more comfortable, and, as accurate as an ERCP detecting a choledocholithiasis.